The first case occurred on May 26. Two more patients came down with infections in June and two more got infections in July.

"What's unusual is to have five in this particular short time frame," said Faith Belcher, a Bay Pines spokeswoman. "What's not unusual is for a dialysis patient to get an infection."

One investigation into the matter already has been completed. A second is under way.

Thus far, officials haven't determined what caused the infections.

Belcher said the infection control department began an initial investigation on July 9, a day after the fifth person was diagnosed. That department routinely monitors the dialysis unit, and had been studying data on the first few patients, Belcher said.

"When that fifth one occurred, they said we really need to look at dialysis," she said. "They could not find any common variables between the five patients."

Bay Pines has 12 dialysis chairs in its unit and averages 34 patients at any given time, Belcher said.

The patients who became infected weren't using the same machine, weren't being cared for by the same nurse and didn't have the same type of bacteria in their blood, Belcher said.

Now, a multidisciplinary team at Bay Pines is doing a second internal investigation called a root cause analysis, which is scheduled to be completed by the end of this month or in September.

Dr. Mark Segal, the chief of the division of nephrology at the University of Florida's Department of Medicine, said being on dialysis is in itself a risk factor of infection.

The procedure, which involves a person being hooked to a machine that removes, cleans and then returns blood to the body, puts a patient's immune system at risk.

It's not uncommon for a dialysis patient to get about one infection per year, Segal said. Infections are a common complication in dialysis units in hospitals, he said.

"When there's a cluster, it's always worrisome, and you want to rule out any procedural issues," he said. "What you're worried about is a systemic issue."

Belcher said there haven't been any other infections in the dialysis unit since July. Those who were infected were treated successfully, she said.

"Based on what we know at this time, we do not believe that the infections are due to patient care at Bay Pines. We're fairly certain that it's not due to processes here," she said. "All of them are now recovered and doing well."

Kameel Stanley can be reached at kstanley@sptimes.com or (727) 893-8643.